1. Field of the Invention
The present invention relates to an improved implement which prevents leakage of microwaves from the housing of a microwave oven by absorbing or reflecting microwaves propagating outward from the housing.
2. Description of the Prior Art
A known means for preventing leakage of microwaves from a microwave oven consists of installing an annular sheet of a synthetic resin on the fringe of the opening of the housing or on the inner surface of the door bearing against the fringe or by installing two such annular sheets on the fringe of the opening and the inner surface of the door. The annular sheets are molded into a form similar to the fringe of the opening. A soft ferrite such as Mn-Zn ferrite or Ni-Zn ferrite is added to the sheets. The annular sheet or sheets are called implements for preventing leakage of microwaves from a microwave oven. The inherent function of a microwave oven is to heat food by microwaves. In recent years, however, an additional device such as an infrared ray-emitting device or steam generator has tended to be installed. Sometimes, even an external heating means such as a gas combustion heat source is added to raise the temperature inside the oven. In this microwave oven, the implement for preventing leakage of microwaves is required to have greater resistance to heat. In addition, moisture resistance and flexibility are needed. Where the conventional implement for preventing leakage of microwaves is made from a synthetic resin such as a nylon, the implement can withstand up to about 180.degree. C. Where the implement is made from a rubber, it can be used up to approximately 150.degree. C. Where the implement is made from polypropylene, it can withstand up to roughly 130.degree. C. When infrared rays or steam is also generated inside a microwave oven, the temperature inside the oven increases to approximately 220.degree.-240.degree. C. The conventional leakage-preventing implement cannot withstand these high temperatures. Accordingly, the use of polyphenylene sulfide which can withstand such high temperatures may be contemplated. Unfortunately, this synthetic resin is brittle and expensive. Especially, a microwave oven having the aforementioned additional function is required to withstand a high temperature of about 230.degree. C. for a short time of about 30 to 60 minutes. Since a leakage-preventing implement of this kind is interposed between the body of a microwave oven and its door, the implement preferably acts to absorb the mechanical shock produced when the door is closed or opened. Additionally, it is necessary that the leakage-preventing implement have flexibility so that it may be easily mounted inside the oven. After the implement has been mounted in the oven, it is desired that no gap be left between the fringe of the opening of the body of the oven and the inner surface of the door. Such a gap is created when hinges used to mount the door to the body chatter or when a foreign matter is introduced. If the gap is formed, microwaves leak through the gap. Therefore, leakage of microwaves cannot be prevented however effectively the leakage-preventing implement absorbs microwaves. As an example, if the gap is in excess of 2 mm, then the capability of the implement to absorb microwaves drops greatly.